A recent meta-analysis published in Aging Clinical and Experimental Research suggests that eating fish may help protect against cognitive decline, dementia, and Alzheimer’s disease. The study found that people who reported eating the most fish were less likely to experience cognitive impairment or decline compared to those who ate the least. However, the findings were strongest for cognitive decline, while more research is needed to firmly establish the link between fish consumption and dementia or Alzheimer’s disease.
The global population is aging rapidly, with more people living longer than ever before. Unfortunately, this increase in life expectancy also brings a rise in age-related health issues, especially cognitive decline, dementia, and Alzheimer’s disease. Worldwide, cases of dementia and Alzheimer’s are expected to triple by 2050, making cognitive health an urgent area of research. Identifying factors that may protect against cognitive decline is crucial, and diet has emerged as one area of interest.
Fish, which is rich in omega-3 fatty acids and other nutrients, has long been thought to benefit brain health. Omega-3s are known to have anti-inflammatory and antioxidant properties, which may help protect the brain from the damage that contributes to cognitive decline. Previous studies have suggested that eating fish is linked to a lower risk of neurodegenerative diseases, but the evidence has been somewhat inconsistent, particularly regarding specific conditions like dementia and Alzheimer’s disease. This new study aimed to update and clarify the current evidence on the association between fish consumption and cognitive health.
“We all know too well the impact of diet on cardio-metabolic health and and certain types of cancer. The relationship between diet and brain health is far less clear, although there is plenty of evidence suggesting that what and how we eat influences our mental well-being,” said study author Giuseppe Grosso, a professor in human nutrition at the University of Catania.
The researchers conducted a meta-analysis, a type of study that combines data from multiple previous studies to look for overall trends. They reviewed observational studies, which had examined the dietary habits of people over the age of 50 and tracked their cognitive outcomes over time. The researchers focused on studies that assessed fish consumption and its relationship to cognitive impairment, dementia, or Alzheimer’s disease.
They included 35 studies in their analysis, involving more than 849,000 participants from around the world. These studies used a variety of methods to assess how much fish people ate, such as food frequency questionnaires and dietary diaries. They also employed different tools to measure cognitive outcomes, including clinical diagnoses of dementia and Alzheimer’s disease as well as assessments of cognitive decline or impairment.
The researchers divided the participants into groups based on how much fish they ate and compared the highest consumers to the lowest consumers. They then calculated risk ratios, a statistical measure that indicates how likely a certain outcome (in this case, cognitive impairment or dementia) is in one group compared to another.
The study found that people who ate the most fish were significantly less likely to experience cognitive decline or impairment compared to those who ate the least. Specifically, the highest fish consumers had an 18% lower risk of cognitive impairment or decline.
“Individuals consuming fish regularly seem to be at lower risk of cognitive decline,” Grosso told PsyPost. “The average person should just take this into account, since many people simply do not eat fish almost at all.”
The researchers also looked at whether there was a dose-response relationship, meaning whether eating more fish led to progressively greater benefits. They found that higher fish consumption was linked to a reduced risk of cognitive impairment, with the most significant reduction observed in people who ate around 150 grams (about 5.3 ounces) of fish per day.
High levels of fish consumption were also associated with an 18% lower risk of dementia and a 15% lower risk of Alzheimer’s disease. But the results for dementia and Alzheimer’s were less conclusive due to variability across the studies, including differences in diagnostic methods and fewer studies focusing on these conditions.
Alzheimer’s is a complex disease with multiple underlying causes, and fish consumption alone may not be enough to prevent its progression. Additionally, the meta-analysis did not find a clear dose-response relationship for dementia or Alzheimer’s, making it harder to confirm a consistent protective effect.
The researchers also conducted subgroup analyses based on genetic variations, specifically looking at people with different forms of the APOE gene, which is known to influence the risk of Alzheimer’s disease. However, the results were mixed, and there were not enough studies to draw firm conclusions. More research is needed to understand how genetic factors might interact with diet to influence cognitive health.
One of the key strengths of this study is that it pooled data from a large number of participants across multiple countries, increasing the generalizability of the findings. However, the researchers also noted a high degree of variability (or “heterogeneity”) between the studies, which may have influenced the results. Some studies showed stronger effects than others, and the reasons for these differences are not entirely clear.
“We need more robust studies: while evidence exists, the heterogeneity between studies weakens the conclusions; hence, more research is needed,” Grosso explained. “Second, we need to clarify the mechanisms: the brain benefits may depend on fats, proteins, or other currently underrated factors. Having certainty about the mechanisms would strengthen the level of evidence.”
“The effects of diet on human health never depend on isolated components,” he noted. “I expect that the association between fish and cognitive health would be optimal when it occurs within the context of an overall healthy and sustainable diet.”
The study, “Fish consumption, cognitive impairment and dementia: an updated dose-response meta-analysis of observational studies,” was authored by Justyna Godos, Agnieszka Micek, Walter Currenti, Carlotta Franchi, Andrea Poli, Maurizio Battino, Alberto Dolci, Cristian Ricci, Zoltan Ungvari, and Giuseppe Grosso.